Law enforcement officers have utilized Doppler-based traffic radar systems to monitor vehicle speeds and enforce traffic speed limit laws for many years. Throughout this period of time, numerous improvements in both the underlying technology and in the specific application of new processing techniques for the traffic radar systems themselves, have afforded law enforcement officers greater flexibility and improved reliability in carrying out their duties. One such improvement evident in most traffic radar systems presently being marketed includes the capability to more accurately and reliably monitor the speed of certain vehicles while the patrol vehicle is either in a stationary or a moving mode of operation. In fact, the recent traffic radar systems can now successfully monitor the speed of vehicles approaching the moving patrol vehicle in an opposite lane.
In addition to these capabilities, such radar systems also provide the law enforcement officer the capability to monitor a group of target vehicles simultaneously and to determine the fastest vehicle within the group and/or the vehicle presenting the traditional strongest reflected return signal. Each of these new or improved existing capabilities provide the law enforcement officer with a more complete picture of the traffic environment and thus, a more flexible and reliable basis for making more informed decisions.
Despite all the improvements in both the underlying technology utilized in these traffic radar systems and the radar systems themselves, a broadly recognized shortcoming of these systems involves the successful monitoring of the speed of vehicles approaching/receding away from the patrol vehicle in the same-lane moving or stationary mode without operator intervention. In practice, even the most recent traffic radar systems require the law enforcement officer to make discretionary decisions regarding the relative movement of a target vehicle operating in the same lane as the patrol vehicle.
In other words, the law enforcement officer must visually observe the target vehicle in front of or behind the patrol vehicle and decide whether the vehicle is approaching or receding relative to the patrol vehicle. Of course, these manual operations are conducted while also maintaining operation of the patrol vehicle. Additionally, the officer must continually input this information into the radar system. Typically, a two-position manual switch located on a display or a handheld remote control device of the radar system is utilized to dictate the approaching/receding status of the target vehicle and to indicate the requisite method of calculation to be utilized by the radar system in determining the actual speed of the target vehicle. These discretionary decisions and required manual operations contribute to the curtailment of the overall flexibility and reliability afforded law enforcement officers by both conventional and digital signal processing (DSP) capable radar systems.
Thus, while conventional and DSP traffic radar systems are both capable of a high degree of accuracy with regard to vehicle speed measurements, great care must be exercised in the use of such systems in properly and accurately attributing a speed to a particular target vehicle. This is of increased importance when the law enforcement officer must initially visually observe the direction of the target vehicle relative to the patrol vehicle traveling in the same lane.
Yet another broadly recognized shortcoming of these traffic radar systems includes the inability to accurately monitor the speeds of vehicles approaching/receding away from the patrol vehicle in the stationary mode of operation in various situations. Typically to overcome this shortcoming, the patrol vehicle must position itself between the driving lanes; for example, within the median area along interstates or other divided highways. This effectively eliminates the unwanted approaching or receding targets from the beam of the radar signal, thus improving the accuracy and reliability afforded the law enforcement officer. The requirement that the patrol vehicle be located in a particular manner, however, severely limits the overall effectiveness of the radar system.
One alternative to establishing a monitoring position within the median of divided roadways presently available to law enforcement officers is to position the patrol vehicle on the shoulder parallel to the highway. This alternative is satisfactory in some settings, particularly along isolated, low volume highways but is of only limited value along the busier and more frequently patrolled highways, such as main traffic arteries. When monitoring vehicle speeds along these highways, the law enforcement officer is forced to wait for openings or gaps in the traffic pattern before utilizing the radar system to determine the speed of approaching/receding opposing lane vehicles. This is due to the potential interference in the radar system processing created by intervening vehicles traveling in the same lane in which the patrol vehicle is positioned.
Accordingly, a need is clearly identified for a radar system and related methods capable of determining the actual speed of a selected target vehicle traveling in the same lane as the moving patrol vehicle, or in a different lane than the stationary patrol vehicle. Such a radar system and related methods would effectively remove the reliance on discretionary decisions made by law enforcement officers in determining the relative direction of target vehicles operating in the same lane as the patrol vehicle, and would further increase the overall flexibility and reliability afforded the system operator, particularly in monitoring traffic across busy divided highways.